Harvey, Is your trailer galvanized?
I would strongly advise a tandem axle trailer if you are doing any serious trailering. Single axle trailers are generally short haul and yard type of trailers for the 22. I had a single axle trailer, which came with one of my 22' and it failed after several years use. The cost differential is not all that much.
The weight difference is several hundred pounds, and depends on both the build quality of both the aluminum frame and galvanized steel frame. The axles, bunks, winch etc are all the same.